net.sf.saxon.expr
Class CastExpression

java.lang.Object
  net.sf.saxon.expr.Expression
      net.sf.saxon.expr.UnaryExpression
          net.sf.saxon.expr.CastExpression

All Implemented Interfaces:

Serializable, SourceLocator, Container, EvaluableItem, SequenceIterable, InstructionInfoProvider

public final class CastExpression
extends UnaryExpression

Cast Expression: implements "cast as data-type ( expression )". It also allows an internal cast, which has the same semantics as a user-requested cast, but maps an empty sequence to an empty sequence.

See Also:

Serialized Form

Field Summary

Fields inherited from class net.sf.saxon.expr.Expression

EVALUATE_METHOD, ITERATE_METHOD, PROCESS_METHOD

Constructor Summary

CastExpression(Expression source, AtomicType target, boolean allowEmpty)

Method Summary

boolean	allowsEmpty()
static AtomicValue	castStringToQName(CharSequence operand, AtomicType targetType, StaticContext env) Evaluate the "pseudo-cast" of a string literal to a QName or NOTATION value.
int	computeCardinality() Get the static cardinality of the expression
int	computeSpecialProperties() Determine the special properties of this expression
boolean	equals(Object other) Is this expression the same as another expression?
Item	evaluateItem(XPathContext context) Evaluate the expression
ItemType	getItemType(TypeHierarchy th) Get the static type of the expression
AtomicType	getTargetPrimitiveType()
AtomicType	getTargetType()
static boolean	isPossibleCast(int source, int target) Determine whether casting from a source type to a target type is possible
boolean	isUpCast()
Expression	simplify(StaticContext env) Simplify the expression
boolean	targetIsDerived()
Expression	typeCheck(StaticContext env, ItemType contextItemType) Type-check the expression

Methods inherited from class net.sf.saxon.expr.UnaryExpression

display, getBaseExpression, hashCode, iterateSubExpressions, optimize, promote, replaceSubExpression

Methods inherited from class net.sf.saxon.expr.Expression

adoptChildExpression, checkPermittedContents, computeDependencies, computeStaticProperties, doPromotion, effectiveBooleanValue, evaluateAsString, getCardinality, getColumnNumber, getContainingProcedure, getDependencies, getExecutable, getHostLanguage, getImplementationMethod, getInstructionInfo, getIntrinsicDependencies, getLineNumber, getLocationId, getLocationProvider, getParentExpression, getPublicId, getSlotsUsed, getSpecialProperties, getSystemId, hasBadParentPointer, iterate, markTailFunctionCalls, process, resetStaticProperties, setLocationId, setParentExpression, setParentExpression, suppressValidation

Methods inherited from class java.lang.Object

getClass, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

CastExpression

public CastExpression(Expression source,
                      AtomicType target,
                      boolean allowEmpty)

Method Detail

isPossibleCast

public static boolean isPossibleCast(int source,
                                     int target)

Determine whether casting from a source type to a target type is possible

Parameters:

source - a primitive type (one that has an entry in the casting table)

target - another primitive type

Returns:

true if the entry in the casting table is either "Y" (casting always succeeds) or "M" (casting allowed but may fail for some values)

getTargetPrimitiveType

public AtomicType getTargetPrimitiveType()

getTargetType

public AtomicType getTargetType()

allowsEmpty

public boolean allowsEmpty()

targetIsDerived

public boolean targetIsDerived()

isUpCast

public boolean isUpCast()

simplify

public Expression simplify(StaticContext env)
                    throws XPathException

Simplify the expression

Overrides:

simplify in class UnaryExpression

Returns:

the simplified expression

Throws:

XPathException - if an error is discovered during expression rewriting

typeCheck

public Expression typeCheck(StaticContext env,
                            ItemType contextItemType)
                     throws XPathException

Type-check the expression

Overrides:

typeCheck in class UnaryExpression

Parameters:

env - the static context of the expression

contextItemType - the static type of "." at the point where this expression is invoked. The parameter is set to null if it is known statically that the context item will be undefined. If the type of the context item is not known statically, the argument is set to Type.ITEM_TYPE

Returns:

the original expression, rewritten to perform necessary run-time type checks, and to perform other type-related optimizations

Throws:

StaticError - if an error is discovered during this phase (typically a type error)

XPathException

computeCardinality

public int computeCardinality()

Get the static cardinality of the expression

Overrides:

computeCardinality in class UnaryExpression

getItemType

public ItemType getItemType(TypeHierarchy th)

Get the static type of the expression

Overrides:

getItemType in class UnaryExpression

Parameters:

th -

Returns:

the item type of the items in the result sequence, insofar as this is known statically.

computeSpecialProperties

public int computeSpecialProperties()

Determine the special properties of this expression

Overrides:

computeSpecialProperties in class UnaryExpression

Returns:

StaticProperty.NON_CREATIVE.

evaluateItem

public Item evaluateItem(XPathContext context)
                  throws XPathException

Evaluate the expression

Specified by:

evaluateItem in interface EvaluableItem

Overrides:

evaluateItem in class Expression

Parameters:

context - The context in which the expression is to be evaluated

Returns:

the node or atomic value that results from evaluating the expression; or null to indicate that the result is an empty sequence

Throws:

XPathException - if any dynamic error occurs evaluating the expression

equals

public boolean equals(Object other)

Is this expression the same as another expression?

Overrides:

equals in class UnaryExpression

castStringToQName

public static AtomicValue castStringToQName(CharSequence operand,
                                            AtomicType targetType,
                                            StaticContext env)
                                     throws XPathException

Evaluate the "pseudo-cast" of a string literal to a QName or NOTATION value. This can only happen at compile time

Returns:

the QName or NOTATION value that results from casting the string to a QName. This will either be a QNameValue or a derived AtomicValue derived from QName or NOTATION

Throws:

XPathException